1. Field of the Invention
The present invention relates to a manufacturing method of a liquid jet head for discharging/flying droplets to attach the droplets to a recording medium.
2. Description of the Related Art
A liquid jet system (ink jet system) is one of so-called non-impact recording systems, and has characteristics that generation of noises at a recording time is small to an ignorable degree, high-speed recording and recording with respect to various recording mediums are possible, the recording is fixed even to a so-called plain paper without requiring any special treatment, and a high-precision image is inexpensively obtained. From these advantages, the head has rapidly spread not only in a printer which is a peripheral apparatus of a computer but also in a printing system such as a copying machine, facsimile, and word processor these several years.
In these days, for liquid discharge methods of a liquid jet apparatus for broad and general use, there have been a method of using an electrothermal conversion element (heater), and a method of using a piezoelectric element (piezo element). In either method, it is possible to control the discharge of the droplets by an electric signal.
For the method in which the electrothermal conversion element is used, when the electric signal is supplied to the electrothermal conversion element, a liquid in the vicinity is momentarily boiled. At this time, bubbles rapidly grow by a phase change of the liquid and the droplets are discharged at a high speed. Therefore, this method has advantages that the structure of the liquid jet head is simple and nozzles are easily integrated. On the other hand, problems peculiar to this method include a volume fluctuation of flied droplets by heat accumulated in the liquid jet head, and adverse influence of cavitation by debubbling onto the electrothermal conversion element.
To solve these problems, for example, there are liquid jet recording methods and liquid jet heads described in Japanese Patent Application Laid-Open Nos. 54-161935, 61-185455, 61-249768, 4-10940, and 4-10941. The liquid jet recording methods described in these are characterized in that the bubbles generated on the electrothermal conversion element in response to a recording signal are communicated with outside air. This is concretely achieved by droplet discharge means in which a distance between the electrothermal conversion element and discharge port is reduced. With the use of such method, enhancement of volume stability of the flied droplets, high-speed small droplets recording, and enhancement of durability of the electrothermal conversion element by elimination of the cavitation are possible, and a highly fine image is easily obtained.
Moreover, in the method in which the piezoelectric element (piezo element) is used, for example, an apparatus constituted of a liquid supply chamber communicated with the liquid discharge port, a pressure chamber communicated with the liquid supply chamber, and a vibration plate which is disposed in the pressure chamber and to which the piezoelectric element is bonded is used. A discharge direction of the liquid and the vibration direction of the piezoelectric element have heretofore been the same. When a predetermined voltage is applied to the piezoelectric element in this constitution, the piezoelectric element expands/contracts. Accordingly, the piezoelectric element and vibration plate cause a drum-shaped vibration, the liquid in the pressure chamber is compressed, and the droplets are accordingly discharged from a liquid discharge port. Therefore, this method using the piezoelectric element does not have volume fluctuation of the flied droplets by the heat accumulated in the liquid jet head or an adverse influence of the cavitation by the debubbling onto the electrothermal conversion element. However, there is a problem that it is difficult to manufacture the liquid jet head with good precision or to integrate the nozzles.
At present, with the spread of the liquid jet apparatus, there has been a demand for enhancement of printing capability, especially a high reliquid and high-speed printing. Therefore, the liquid jet head has been miniaturized and a multi nozzle head structure has been used to make an attempt to realize the high reliquid and high-speed printing.
In the method using the electrothermal conversion element, it is easy to miniaturize/process the head. Moreover, there has similarly been a strong demand for miniaturization of the head of the piezoelectric element by the fine processing of the head. For the miniaturization of the piezoelectric element, a method of reducing the thickness of a piezoelectric material, using the vibration plate to generate deflection vibration, and discharging the liquid is structurally possible. However, displacement of the piezoelectric material itself with respect to the voltage is very small. Therefore, when the piezoelectric element is miniaturized, sufficient stress or vibration is not generated from the drop of a piezoelectric property and the liquid cannot be discharged. Then, in order to realize the high reliquid and high-speed recording including the small-sized multi nozzle head, attempts have been made to develop a piezoelectric thin film material which has a sufficient piezoelectric property even in a small film thickness and to establish the manufacturing method.
Especially, in the piezoelectric material of a sintered material which has heretofore been used, the device has been miniaturized by mechanical processing such as cutting. However, there is a limitation in the miniaturization by the mechanical processing, deterioration of the piezoelectric property is caused, and it has been difficult to establish both the miniaturization and the high reliquid.
On the other hand, to solve the problem of the piezoelectric element including a conventional sintered material, in Japanese Patent Application Laid-Open No. 10-286953, a constitution and manufacturing method have been proposed in which the thickness of the piezoelectric material or the vibration plate constituting the piezoelectric element is reduced so as to obtain such a shape that the fine processing generally used in a semiconductor process is possible. Furthermore, a thin film material having a large piezoelectric characteristic even with the small film thickness is developed, and a high-density structure of the nozzles is realized.
However, according to the manufacturing process proposed in the Japanese Patent Application Laid-Open No. 10-286953, the thickness of the piezoelectric material or the vibration plate constituting the piezoelectric element is reduced, and the semiconductor process is used to perform the fine processing. However, any concrete manufacturing method has not been disclosed with respect to the forming of the liquid jet head which is a device.
In the liquid jet head, in order to realize the miniaturization, the high reliquid including the multi nozzle head, and high-speed recording, it has been an important problem to prepare a structure in which not only the piezoelectric element but also the nozzle structure, pressure chamber, and liquid supply path can be optimized/designed and the droplets can be controlled with good precision.